It is known in the art that imaging display materials are utilized for advertising, as well as decorative displays of images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters, and fine art photography. The desired attributes of a quality, high impact display material are a slight blue density minimum, durability, sharpness, and flatness. Cost is also important, as photographic display materials tend to be expensive as the imaging process is equipment intensive and requires processing chemicals. For imaging display materials, traditional paper bases are undesirable, as they suffer from a lack of durability for the handling and captured display of large format images. The use of display materials such as lithographic prints or ink jet prints could be expanded if image quality was improved.
In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult, requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. The formation of a suitably smooth surface would also improve image quality, as the display material would have more apparent blackness as the reflective properties of the improved base are more specular than the prior materials. As the whites are whiter and the blacks are blacker, there is more range in between and, therefore, contrast is enhanced. It would be desirable if a more reliable and improved surface could be formed at less expense.
Prior art photographic reflective papers comprise a melt extruded polyethylene layer, which also serves as a carrier layer for optical brightener and other whitener materials, as well as tint materials. It would be desirable if the optical brightener, whitener materials and tints, rather than being dispersed in a single melt extruded layer of polyethylene, could be concentrated nearer the surface where they would be more effective optically.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin coated clear polyester sheet. Incorporated diffusers are necessary to diffuse the light source used to illuminate transmission display materials. Without a diffuser, the light source would reduce the quality of the image. Typically, white pigments are coated in the bottommost layer of the imaging layers. Since light sensitive silver halide emulsions tend to be yellow because of the gelatin used as a binder for photographic emulsions, minimum density areas of a developed image will tend to appear yellow. Further, image receiving layers common to digital printing technology also use materials that have a native color. An example is gelatin used in ink jet image receiving layers. A yellow density minimum reduces the commercial value of a transmission display material because the image viewing public associates image quality with a white or slight blue density minimum area. It would be desirable if a transmission display material with an incorporated diffuser could have a slight blue tint.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin subbed clear polyester sheet. TiO.sub.2 is added to the bottommost layer of the imaging layers to diffuse light so well that individual elements of the illuminating bulbs utilized are not visible to the observer of the displayed image. However, coating TiO.sub.2 in the imaging layer causes manufacturing problems such as increased coating coverage which requires more coating machine drying and a reduction in coating machine productivity, as the TiO.sub.2 requires additional cleaning of the coating machine. Further, as higher amounts of TiO.sub.2 are used to diffuse high intensity backlighting systems, the TiO.sub.2 coated in the bottommost imaging layer causes unacceptable light scattering reducing the quality of the transmission image. It would be desirable to eliminate the TiO.sub.2 from the image layers while providing the necessary transmission properties and image quality properties.
Prior art photographic transmission display materials, while providing excellent image quality, tend to be expensive when compared with other quality imaging technologies such as ink jet imaging, thermal dye transfer imaging, and gravure printing. Since photographic transmission display materials require an additional imaging processing step compared to alternate quality imaging systems, the cost of a transmission photographic display can be higher than other quality imaging systems. The processing equipment investment required to process photographic transmission display materials also requires consumers to typically interface with a commercial processing lab increasing time to image. It would be desirable if a high quality transmission display support could utilize nonphotographic quality imaging technologies.
Photographic transmission display materials have considerable consumer appeal as they allow images to be printed on high quality support for home or small business use. Consumer use of photographic display materials generally have been cost prohibitive since consumers typically do not have the required volume to justify the use of such materials. It would be desirable if a high quality transmission display material could be used in the home without a significant investment in equipment to print the image.
Prior art photographic display materials use polyester as a base for the support. Typically the polyester support is from 150 to 250 .mu.m thick to provide the required stiffness. A thinner base material would be lower in cost and allow for roll handling efficiency, as the rolls would weigh less and be smaller in diameter. It would be desirable to use a base material that had the required stiffness but was thinner to reduce cost and improve roll handling efficiency.